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Towards a Standardized Federate Protocol for HLA 4

ABSTRACT: HLA is a powerful interoperability standard with a rich set of services for information exchange, synchronization and management of federations. These services are accessed through a local RTI library, installed on the same computer as the simulation itself. As new and improved RTI versions are released, or if the user wants to switch RTI supplier, these libraries need to be replaced. What if there were instead a simple protocol that a simulation could use to access the HLA services?


This paper proposes such a protocol for HLA 4. It partly builds on experiences from the Web Services API in HLA Evolved. The WS API proves the concept, but has several shortcomings dues to its use of blocking calls and use of XML. An optimized, streaming, binary protocol is instead suggested. Such a protocol would make it easy to add a small and
generic library to any federate. Switching RTI libraries would then be a simple operation of connecting to a different network address.

Additional advantages are that it makes it easy to provide native HLA support for any language, like C# or Python, to execute in CPU-constrained or hard real-time environments, to communicate in mobile environments, like 3G or 4G, or even to embed HLA support in hardware equipment. It can also be used to avoid re-accreditation of simulations, since the accredited simulator need not be updated. Some design considerations include discovery, session management and latency handling. Early test implementations have shown performance close to current RTI performance and improved fault tolerance over WAN links. To be able to easily swap between different RTI implementations, a standardized protocol is now being proposed to the HLA 4 Product Development Group.

Authors: Björn Möller, Mikael Karlsson, Fredrik Antelius
Publication: Proceedings of 2018 Winter Simulation Interoperability Workshop, 18W-SIW-037, Simulation Interoperability Standards Organization, January 2018

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Evolving Standards for Tactical Data Link Aware Simulators

ABSTRACT: The ability to simulate Tactical Data Links is becoming increasingly important in order to more accurately represent the modern battlespace. There is also a need to be able to connect with or simulate commercial use data links such as ADS­B and AIS. LVC applications may rely on the integration between simulation systems and real data links in order to integrate live entities into a simulated scenario in applications ranging from test and evaluation to training. There is also a growing number of COTS simulation tools available that support integration with
data links.


This paper will discuss the need for inclusion of a data link FOM module in the upcoming RPR­FOM v 3.0 which supports various data links such as Link 11, Link 16 and the upcoming Link 22. The paper also discusses the need for supporting a more generic interaction with data links that would enable integration of various simulation CGF components with less effort and enable COTS tools to evolve with a broader support for dif erent data links.

Authors: Patrik Svensson, Stefan Sandberg, Fredrik Antelius, Laurent Ferriani, Laurent Mounet
Publication: Proceedings of 2016 Fall Simulation Interoperability Workshop, 2016-SIW-042, Simulation Interoperability
Standards Organization, September 2016

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A First Look at the Upcoming SISO Space Reference FOM

SISO SIWzie award winner

ABSTRACT: Spaceflight is difficult, dangerous and expensive; human spaceflight even more so. In order to mitigate some of the danger and expense, professionals in the space domain have relied, and continue to rely, on computer simulation. Simulation is used at every level including concept, design, analysis, construction, testing, training and ultimately flight. As space systems have grown more complex, new simulation technologies have been developed, adopted and applied. Distributed simulation is one of those technologies.

Distributed simulation provides a base technology for segmenting these complex space systems into smaller, and usually simpler, component systems or subsystems. This segmentation also supports the separation of responsibilities between participating organizations. This segmentation is particularly useful for complex space systems like the International Space Station (ISS), which is composed of many elements from many nations along with visiting vehicles from many nations. This is likely to be the case for future human space exploration activities. Over the years, a number of distributed simulations have been built within the space domain. While many use the High Level Architecture (HLA) to provide the infrastructure for interoperability, HLA without a Federation Object Model (FOM) is insufficient by itself to insure interoperability.

As a result, the Simulation Interoperability Standards Organization (SISO) is developing a Space Reference FOM. The Space Reference FOM Product Development Group is composed of members from several countries. They contribute experiences from projects within NASA, ESA and other organizations and represent government, academia and industry. The initial version of the Space Reference FOM is focusing on time and space and will provide the following: (i) a flexible positioning system using reference frames for arbitrary bodies in space, (ii) a naming convention for wellknown reference frames, (iii) definitions of common time scales, (iv) federation agreements for common types of time management with focus on time stepped simulation, and (v) support for physical entities, such as space vehicles and astronauts.

The Space Reference FOM is expected to make collaboration politically, contractually and technically easier. It is also expected to make collaboration easier to manage and extend.

Authors: Björn Möller, Edwin Z Crues, Dan Dexter, Alfredo Garro, Anton Skuratovskiy, Alexander Vankov
Publication: Proceedings of 2016 Fall Simulation Interoperability Workshop, 2016-SIW-017, Simulation Interoperability
Standards Organization, September 2016

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Building Scalable Distributed Simulations: Design Patterns for HLA DDM

ABSTRACT: Over the last decades the size of scenarios in distributed simulation has grown considerably, for example in defense training. There is also a demand for larger number of federates within exercises. This means that federation scalability is an area of growing importance. The developers of HLA foresaw this and introduced not only class-based
filtering, but also the HLA Data Distribution Management (DDM) for instance filtering. This is a very general and flexible mechanism for filtering.

The challenge for many beginners has been to understand DDM and to develop efficient designs. This paper presents some design patterns for DDM and discusses their pros and cons as well as implementation and
efficiency. One design pattern is Uniform DDM where all attributes of an object class have the same DDM dimensions available. This makes the use of DDM much easier in federations. Design patterns for filtering based on static properties (like the fuel type of a vehicle) and dynamic properties (like the position of a vehicle) are then covered.

A number of best-practices are also discussed, for example FOM design, handling of objects going in and out of scope as well as the usefulness of advisories. Life cycle challenges, like how to mix federates with and without DDM support are covered.

Finally, some thoughts are given on the design of general and reusable DDM schemes. As an example a number of DDM schemes are proposed for the RPR FOM.

Authors: Björn Möller, Fredrik Antelius, Martin Johansson, Mikael Karlsson
Publication: Proceedings of 2016 Fall Simulation Interoperability Workshop, 2016-SIW-003, Simulation Interoperability
Standards Organization, September 2016

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Towards RPR FOM 3: Revisiting the Datatypes

ABSTRACT: Version 2 of the Real-time Platform Reference FOM (RPR FOM) has recently been finalized. It is the most widely used FOM for defense simulations. The original purpose of the RPR FOM was to facilitate interoperability between the DIS protocol and HLA federations. Today it is often also used as a common basis for further adaptation and extensions in US and NATO federations.


One of the main goals of the final phase of the RPR FOM 2 development was to maintain buffer compatibility with the widely used draft 17 of the RPR FOM 2. This in turn carries a lot of heritage from both the DIS protocol and the HLA version 1.3, including many convoluted data buffer layouts. Today these may not be seen as striking the best balance between low bandwidth utilization, simple encoding and decoding, flexibility and extensibility.


Now the time may have come to revisit the RPR FOM data representations for RPR FOM version 3. In addition to the
reviewing the record data structures, a goal could be to remove the RPR FOM specific datatype encodings such as the length less array representations. Furthermore, an attempt to generate the Enumerations module from the SISO-REF010 XML source showed that some enumerations may need to be reconsidered or moved to other modules. The RPR FOM 2 work has also revealed that some new datatypes may need to be added to the HLA standard, in particular to represent unsigned integers that are used in DIS.


This paper provides an analysis and recommendation for the RPR FOM 3 development and to some extent for the next version of HLA.

Authors: Björn Möller, Aaron Dubois, Patrice Le Leydour, Graham Shanks, René Verhage, Fredrik Antelius
Publication: Proceedings of 2015 Fall Simulation Interoperability Workshop, 15F-SIW-039, Simulation Interoperability
Standards Organization, September 2015

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Using HLA Object Models for the Analysis of Cross Domain Security Policies

ABSTRACT: Across defence, training equipment, data and scenarios are likely to have different classification levels. Thus it is sometimes necessary for training to be carried out using a federation of participating systems
running at different classification levels, but without compromising security rules. This is usually done using guards and filters to limit the data that may be released from the higher security domain to the lower security
domain. In some cases, limiting the data may negatively impact the training and make it impossible to meet all the training goals. When following the process from design to security accreditation it is crucial to understand
how to meet security requirements while also understanding the impact this will have on the training.


This paper suggests an approach based on a description of the data exchange using the object models of the High Level Architecture. One type of object model is the Federation Object Model (FOM). It specifies the type and format of any data exchanged in the federation. This includes descriptions of objects (such as aircraft, soldiers and weapons) and interactions (such as orders, fire and detonation). Another type of object model is the Simulation Object Model (SOM). This is used to describe which objects and interactions are published (produced) and subscribed (consumed) by any one simulation system. The proposed method uses the SOMs to analyse the data flow within and between the different security domains.


It allows the user to suggest different security policies. It then provides an automatic analysis that can be used to analyse the effect from both training and security perspective. This analysis can be performed for standard
FOMs, like RPR FOM and NATO NETN FOM as well as extensions of these and project specific FOMs.


The proposed method can be used as a basis for a dialog between accreditors and developers of training federations. This can help to avoid security issues, to understand the impact of training goals and also to detect any technical issues that may be introduced by the presence of a guard.

Authors: Björn Möller, Stella Croom-Johnson, Åsa Falkenjack, Kester Hughes
Publication: Proceedings of 2015 Fall Simulation Interoperability Workshop, 15F-SIW-038, Simulation Interoperability Standards Organization, September 2015.

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An update on the developments and maturity of the NATO Education and Training Network (NETN) Federation Architecture and Federation Object Model (FOM)

Authors: Michael Mifsud, Björn Löfstrand, Jon Lloyd.
Publication: NATO Modelling and Simulation Group (NMSG) Multi-Workshop [MSG-126], STO-MP-MSG-126-022

NATO Website

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Meeting the NATO M&S Interoperability Challenge.

Authors: Wim Huiskamp, Adrian Voiculet, Erdal Cayirci, Björn Löfstrand, Bharat Patel, Lionel Khimeche, Kevin Heffner, Nico de Reus, Jean-Louis Igarza, Jeroen Voogd, Manfred Roza, Niels Krarup-Hansen.
Publication: M&S Journal 07/2014; 9(2):16

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A Common Chemical, Biological & Radiological modelling capability: UK and NATO HLA-Evolved experimentation

ABSTRACT: The United Kingdom (UK) Ministry of Defence’s (MOD) Defence Science and Technology Laboratory (Dstl) have sponsored two key development activities relating to the OneSAF Computer Generated Forces (CGF) system and development of a Common Chemical, Biological and Radiological (CBR) modelling capability. The first is an interface to enable OneSAF to operate in a High Level Architecture (HLA) 1516-2010 (HLA Evolved) federation.

The second is an extension to the North Atlantic Treaty Organisation (NATO) Education and Training Network (NETN) Federation Object Model (FOM) to support CBR interoperability. This acts as an enabler for CBR M&S services to be provided to Live, Virtual and Constructive (LVC) simulation systems by a common CBR modelling capability. Although individually these two developments have much broader application, this paper presents a use case bringing the two together to demonstrate CBR federate interoperability with OneSAF and how this has been standardised, developed and experimented using support from the NATO Modelling and Simulation Community

Authors: Jon Lloyd, Nathan Newton, Russell Mills, David Désert, José Ruiz, Antony Hubervic, Lennart Olsson.
Publication: Proceedings of 2014 Fall Simulation Interoperability Workshop, 14F-SIW-021, Simulation Interoperability Standards Organization, September 2014.

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RPR FOM 2.0: A Federation Object Model for Defense Simulations

SISO SIWzie award winner

ABSTRACT: The Real-Time Platform Reference Federation Object Model (RPR FOM) is the most widely used FOM for defense simulations. The main focus is on real-time simulation of war fighting scenarios including platforms, humans and weapons, however many related interactions such as radio, logistics and synthetic environments are also included. Version 1.0 of the RPR FOM was published in 1999; following this release the development of version 2.0 started. After having published developed several drafts, one of which was known as version 2 draft 17 and was widely used, the development slowed down. But in 2011 the work was revived. The earlier draft standard has now been overhauled and modernized.

This includes fixing many issues, providing FOM versions in the newer, modular FOM format and revising the documentation, known as the GRIM. This paper describes the major updates of the new standard as well as experiences from drafting and standardizing this new FOM version. We believe that the finalized RPR FOM will be of great value to governments, end users and vendors. Technically it establishes a good baseline for interoperability in defense and security training. Policy-wise it provides a vendorneutral standard, developed in consensus by government, industry and academia. Long-term it provides a solid platform for the development of future FOM versions and for inclusion in national and international training architectures.

Authors: Björn Möller, Aaron Dubois, Patrice Le Leydour, René Verhage
Publication: Proceedings of 2014 Fall Simulation Interoperability Workshop, 14F-SIW-039, Simulation Interoperability Standards Organization, September 2014.

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